Doping with solid-state diffusion sources for finfet architectures

ABSTRACT

An impurity source film is formed along a portion of a non-planar semiconductor fin structure. The impurity source film may serve as source of an impurity that becomes electrically active subsequent to diffusing from the source film into the semiconductor fin. In one embodiment, an impurity source film is disposed adjacent to a sidewall surface of a portion of a sub-fin region disposed between an active region of the fin and the substrate and is more proximate to the substrate than to the active area.

CLAIM OF PRIORITY

This United States continuation patent application is related to, andclaims priority to, U.S. patent application Ser. No. 14/914,614 entitled“ISOLATION WELL DOPING WITH SOLID-STATE DIFFUSION SOURCES FOR FINFETARCHITECTURES,” filed February 25, 2016, the entire contents of whichare incorporated herein by reference, and to corresponding InternationalPatent Application No. PCT/US13/61732 entitled “ISOLATION WELL DOPINGWITH SOLID-STATE DIFFUSION SOURCES FOR FINFET ARCHITECTURES,” filed Sep.25, 2013, the entire contents of which are also incorporated herein byreference.

TECHNICAL FIELD

Embodiments of the invention generally relate to integrated circuits(ICs), and more particularly pertain to well impurity doping of FinFETs.

BACKGROUND

Monolithic ICs generally comprise a number of transistors, such asmetal-oxide-semiconductor field-effect transistors (MOSFETs) fabricatedover a planar substrate, such as a silicon wafer. System-on-a-chip (SoC)architectures utilize transistors in both analog and digital circuitry.Monolithic integration of high-speed analog and digital circuitry can beproblematic, in part, because digital switching can induce substratenoise that can limit precision and linearity of analog circuitry.Greater substrate isolation is therefore advantageous for improved SoCperformance.

FIG. 1A illustrates an arrangement of a monolithic device structure 101that may be employed to measure substrate isolation between a first port(Port 1) and a second port (Port 2). Generally, a signal S₁ is appliedto Port 1 and strength of a corresponding noise signal S₂ is measured atPort 2 with isolation defined as the ratio of the two signal strengths(S₂/S₁). Guard ring structures, such as guard ring 110, and wellisolation structures, such as deep well 120, may be provided to improvesubstrate isolation. As shown, guard ring 110 forms P/N/P impurity typeregions ensuring a reversed diode surrounds any noise sensitivecircuitry (e.g., one or more transistors of analog circuitry). Suchguard ring structures may improve isolation by 20 dB, or more. Substrateisolation can be further improved with the exemplary deep well 120,which includes an n-type region disposed below a p-well (e.g., in whichn-type transistors might be disposed) within guard ring 110. The n-typeregions of guard ring 110 and deep well 120 may be made continuous, asoften found in a triple-well process, to further improve substrateisolation between Ports 1 and 2. Such deep well isolations may improveisolation by 35 dB, or more, relative to a guard ring structure alone.

Deep well structures are typically fabricated through ion implantation,for example with a high-energy phosphorus implant for an n-well. Highenergy is required to achieve sufficient well depth, which may behundreds of nanometers below a top surface of the substrate,particularly where the overlying active device silicon has a non-planar(e.g., finFET) architecture 102, as depicted in FIG. 1B. Such implantprocesses however can damage overlying active device silicon 150 and arealso associated with implanted species concentration profiles that canbe a limiter of device scaling.

Device structures and techniques for well doping which offer goodisolation and are amenable to non-planar device architectures wouldtherefore be advantageous.

BRIEF DESCRIPTION OF THE DRAWINGS

The material described herein is illustrated by way of example and notby way of limitation in the accompanying figures. For simplicity andclarity of illustration, elements illustrated in the figures are notnecessarily drawn to scale. For example, the dimensions of some elementsmay be exaggerated relative to other elements for clarity. Further,where considered appropriate, reference labels have been repeated amongthe figures to indicate corresponding or analogous elements. In thefigures:

FIG. 1A is a cross-sectional view of a conventional structure forassessing a level of isolation between to two regions in of a monolithicsemiconductor device;

FIG. 1B is a cross-sectional view of a conventional structure depictingconvention implantation technique for forming an isolation well in asub-fin region of a monolithic semiconductor device;

FIG. 2A is a plan view of an integrated microelectronic device having afinFET architecture with solid-state diffusion sources for isolationwell doping, in accordance with an embodiment;

FIG. 2B is a cross-sectional view along the B-B′ plane depicted in theintegrated microelectronic device of FIG. 2A, in accordance with anembodiment;

FIG. 2C is a cross-sectional view along the C-C′ plane depicted in theintegrated microelectronic device of FIG. 2A, in accordance with anembodiment;

FIG. 2D is a cross-sectional view along the D-D′ plane depicted in theintegrated microelectronic device of FIG. 2A, in accordance with anembodiment;

FIG. 3 is a flow diagram illustrating methods of forming an integratedmicroelectronic device having a finFET architecture with solid-statediffusion sources for isolation well doping, in accordance withembodiments;

FIG. 4 is a flow diagram further illustrating methods of forming anintegrated microelectronic device having a finFET architecture withmultiple solid-state diffusion sources for well doping, in accordancewith embodiments;

FIGS. 5A, 5B, 5C, 5D, 5E, 5F, 5G, 5H, 5I, and 5J are cross-sectionalviews of an evolving finFET as particular fabrication operationsillustrated in FIG. 4 are performed to arrive at the architectureillustrated in FIG. 2A, in accordance with an embodiment;

FIG. 6 illustrates a mobile computing platform and a data server machineemploying a monolithic IC with isolation impurity source films adjacentto a portion of a sub-fin region of a finFET, in accordance withembodiments of the present invention; and

FIG. 7 is a functional block diagram of an electronic computing device,in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

One or more embodiments are described with reference to the enclosedfigures. While specific configurations and arrangements are depicted anddiscussed in detail, it should be understood that this is done forillustrative purposes only. Persons skilled in the relevant art willrecognize that other configurations and arrangements are possiblewithout departing from the spirit and scope of the description. It willbe apparent to those skilled in the relevant art that techniques and/orarrangements described herein may be employed in a variety of othersystems and applications other than what is described in detail herein.

Reference is made in the following detailed description to theaccompanying drawings, which form a part hereof and illustrate exemplaryembodiments. Further, it is to be understood that other embodiments maybe utilized and structural and/or logical changes may be made withoutdeparting from the scope of claimed subject matter. It should also benoted that directions and references, for example, up, down, top,bottom, and so on, may be used merely to facilitate the description offeatures in the drawings and are not intended to restrict theapplication of claimed subject matter. Therefore, the following detaileddescription is not to be taken in a limiting sense and the scope ofclaimed subject matter is defined solely by the appended claims andtheir equivalents.

In the following description, numerous details are set forth, however,it will be apparent to one skilled in the art, that the presentinvention may be practiced without these specific details. In someinstances, well-known methods and devices are shown in block diagramform, rather than in detail, to avoid obscuring the present invention.Reference throughout this specification to “an embodiment” or “oneembodiment” means that a particular feature, structure, function, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the invention. Thus, the appearances ofthe phrase “in an embodiment” or “in one embodiment” in various placesthroughout this specification are not necessarily referring to the sameembodiment of the invention. Furthermore, the particular features,structures, functions, or characteristics may be combined in anysuitable manner in one or more embodiments. For example, a firstembodiment may be combined with a second embodiment anywhere theparticular features, structures, functions, or characteristicsassociated with the two embodiments are not mutually exclusive.

As used in the description of the invention and the appended claims, thesingular forms “a”, “an” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willalso be understood that the term “and/or” as used herein refers to andencompasses any and all possible combinations of one or more of theassociated listed items.

The terms “coupled” and “connected,” along with their derivatives, maybe used herein to describe functional or structural relationshipsbetween components. It should be understood that these terms are notintended as synonyms for each other. Rather, in particular embodiments,“connected” may be used to indicate that two or more elements are indirect physical, optical, or electrical contact with each other.“Coupled” may be used to indicated that two or more elements are ineither direct or indirect (with other intervening elements between them)physical, optical, or electrical contact with each other, and/or thatthe two or more elements co-operate or interact with each other (e.g.,as in a cause an effect relationship).

The terms “over,” “under,” “between,” and “on” as used herein refer to arelative position of one component or material layer with respect toother components or layers where such physical relationships arenoteworthy. For example in the context of material layers, one layerdisposed over or under another layer may be directly in contact with theother layer or may have one or more intervening layers. Moreover, onelayer disposed between two layers may be directly in contact with thetwo layers or may have one or more intervening layers. In contrast, afirst layer “on” a second layer is in direct contact with that secondlayer. Similar distinctions are to be made in the context of componentassemblies.

As used in throughout this description, and in the claims, a list ofitems joined by the term “at least one of” or “one or more of” can meanany combination of the listed terms. For example, the phrase “at leastone of A, B or C” can mean A; B; C; A and B; A and C; B and C; or A, Band C.

As will be described in greater detail below, at least one impuritysource film is formed along a portion of a non-planar semiconductor finstructure. The impurity source film may serve as a source of at leastone type of impurity that becomes electrically active subsequent todiffusing from the source film into the semiconductor fin. In one suchembodiment, an impurity source film is disposed adjacent to a sidewallsurface of a portion of a sub-fin region disposed between an activeregion of the fin and the substrate and is more proximate to thesubstrate than to the active area. In further embodiments, the impuritysource film may provide a source of dopant that renders the sub-finregion complementarily doped relative to a region of the substrateforming a P/N junction that is at least part of an isolation structureelectrically isolating the active fin region from a region of thesubstrate.

As will also be described in greater detail below, an integratedmicroelectronic device having a finFET architecture may rely onsolid-state diffusion sources where an impurity source film is formedadjacent to a sidewall of a portion of a sub-fin region proximate tosubstrate. A second film may be formed over the impurity source film tobe adjacent to a sidewall of a portion of the sub-fin region moreproximate to the active region than to the substrate. The second filmmay be an undoped isolation dielectric or a second impurity source film.Dopants are driven from the impurity source film(s) into the portions ofthe sub-fin region proximate to the source films. A gate stack andsource/drain are then formed for the active region of the fin.

In embodiments, an integrated microelectronic device includes asubstrate and a plurality of transistors disposed on the substrate. Atleast one transistor includes a non-planar semiconductor fin extendingfrom the substrate (i.e., a finFET). FIG. 2A is a plan view of anintegrated microelectronic device 200 having transistors with a finFETarchitecture and relying, at least in part, on solid-state diffusion forisolation well doping, in accordance with an embodiment. Microelectronicdevice 200 is disposed on substrate 205, which may be any substrateknown in the art to be suitable for forming an IC, such as, but notlimited to, a semiconductor substrate, semiconductor-on-insulator (SOI)substrate, or an insulator substrate (e.g., sapphire), the like, and/orcombinations thereof. In one exemplary embodiment, substrate 205comprises a substantially monocrystalline semiconductor, such as, butnot limited to, silicon. While substrate 205 may be of either n-type orp-type conductivity, in the exemplary embodiment substrate 205 hasp-type conductivity and may include a resistive p-type silicon epitaxiallayer disposed on a non-intentionally doped silicon substrate. Extendingfrom first substrate region 211 are non-planar semiconductor bodies, or“fins” 201, 202 and extending from second substrate region 212 are fins203, and 204. Fins 201-204 are advantageously substantiallymonocrystalline, and have the same crystal orientation as substrate 205.Polycrystalline fin embodiments are however also possible as embodimentsof the invention are not notably limited by either the microstructure orcomposition of fins 201-204. Fins 201-204 may all have the samesemiconductor compositions or differ between them. Furthermore, one ormore fin may comprise an epitaxial layered structure or be of ahomogeneous semiconductor. Exemplary semiconductor compositions includegroup IV systems, such as silicon, germanium, or an alloy thereof, orgroup III-V systems, such as GaAs, InP, InGaAs, and the like, or groupIII-N systems, such as GaN. Within each substrate region 211, 212 anisolation dielectric 208 is disposed between fins 201-204. Isolationdielectric 208 may have any conventional composition, such as, but notlimited, to, one or more layers of one or more of silicon dioxide,silicon oxynitride, or silicon nitride.

As illustrated in FIGS. 2B and 2C, fins 201 and 202 are of a same,homogeneous semiconductor. For such embodiments where substrate 205 issubstantially monocrystalline silicon, fins 201-202 are substantiallymonocrystalline silicon that is contiguous with substrate 205 (i.e., nointervening layer of distinct material composition). Fins 201-204 maytake a wide variety of structural forms and dimensions. In the exemplaryembodiment, fins 201, 202 include sidewall surfaces that arenon-parallel (e.g., along a y-z plane in FIG. 2B and an x-z plane inFIG. 2C) to plane of the substrate surface (e.g., along an x-y plane)and a top surface that may be rounded or may be substantially planarwith a top surface of the substrate. In certain embodiments, fins 201,202 have a lateral fin width (W_(fin)) less than 50 nm, advantageouslyless than 30 nm, and more advantageously less than 20 nm. In certainsuch embodiments, fins 201, 202 further extend from substrate 205 by avertical height (H_(fin)) that is less than 200 nm, advantageously lessthan 150 nm, and more advantageously between 20 nm and 150 nm. A lengthof fins 201, 202 (L_(fin) in FIG. 2C) is arbitrary as a function ofprocess capability and parametric requirements, etc. Fins 203-204 mayhave substantially the same fin dimensions as fins 201, 202.

In embodiments, semiconductor fins include an active region where thetransistor channel and source/drain semiconductor resides. As shown inFIGS. 2B and 2C, fins 201, 202 are divided into portions along thez-height of the fin, each portion have a z-height less than the totalfin height H_(fin). The active region of fins 201, 202 is associatedwith an incremental fin sidewall height H₃. Electrically coupled to theactive fin region is a gate stack 260, which for example includes a gatedielectric (e.g., silicon dioxide, and/or silicon nitride, and/orsilicon oxynitride, and/or a higher-K material like HfO₂, or the like),and a gate electrode, which may be any conventional material, such as,but not limited to, polysilicon and/or one or more metals. On oppositesides of gate stack 260 are source/drain contacts 255 coupling tosource/drain semiconductor regions of fins 201-204.

In embodiments, a semiconductor fin further includes a sub-fin regiondisposed between the active region of the fin and the substrate. Inembodiments, at least a portion of sub-fin region is doped with one ormore electrically active impurity. For fin 201, the sub-fin regionincludes a lower sub-fin region 210A proximate to substrate 205 andassociated with an incremental fin sidewall height H₁. Fin 202, includesan analogous lower sub-fin region 210B. In the exemplary embodiment,lower sub-fin regions 210A, 210B are impurity doped with one or moreelectrically active impurity, such as but not limited to phosphorus,arsenic (n-type dopants of silicon) and boron (p-type dopant ofsilicon), although any conventional dopant species may be selecteddepending on the semiconductor material system (e.g., aluminum for GaNsystems, etc.). In further embodiments, lower sub-fin regions 210A, 210Bhave substantially the same impurity and impurity concentration. Inexemplary silicon fin embodiments, lower sub-fin regions 210A, 210B havean impurity concentration of between 10¹⁷ cm⁻³ and 10¹⁹ cm⁻³. In onesuch embodiment, lower sub-fin regions 210A, 210B have a conductivitytype opposite that of substrate 205. For example, where substrate 205 isp-type, the lower sub-fin regions 210A, 210B are n-type (e.g., withphosphorus impurity between 10¹⁷ cm⁻³ and 10¹⁹ cm⁻³). As such, lowersub-fin regions 210A, 210B may function as a deep counter-doped “well”(e.g., an n-well) providing isolation to overlying active region of thefins 201, 202.

In embodiments, a surface layer of the substrate between two impuritydoped lower sub-fin regions is also impurity doped distinctly from asub-surface region of substrate that is disposed below the substratesurface layer. Referring to FIG. 2B, substrate surface layer 206 hassubstantially the same impurity dopant concentration as sub-regions210A, 210B (e.g., 10¹⁷cm⁻³−10¹⁹cm⁻³). In further embodiments, thethickness of substrate surface layer 206 (T_(s)) is no greater than thelateral width (W_(fin)) of semiconductor fins 201, 202, and isadvantageously between 50% and 100% of W_(fin). As further illustratedin FIGS. 2A and 2D, surface layer 206 is absent from substrate region212 and therefore is present between only a subset of fins 201-204.

In embodiments, an integrated microelectronic device includes a firstimpurity source film disposed adjacent to a sidewall surface of thelower sub-fin region. For such embodiments, the impurity source film maybe utilized as a source of impurities for doping the lower sub-finregion by solid-state diffusion. As shown in FIG. 2A, a first impuritysource film 215 is disposed adjacent to opposing sidewalls of fins 201,202, and more specifically in direct contact with fin semiconductor. Inother embodiments however, an intervening material layer may be disposedbetween an impurity source film and fin semiconductor. Impurity sourcefilm 215 extends from a top surface of substrate 205 to approximatelyH₁, which may range from the only the thickness of impurity source film215 (e.g., 1-5 nm) up through an arbitrarily high percentage of the finheight H_(fin).

As further shown in FIG. 2B, impurity source film 215 is furtherdisposed over (e.g., in direct contact with) substrate surface layer206. Impurity source film 215 may have a wide range of thicknesses, butin exemplary embodiments where W_(fin) is less than 20 nm, impuritysource film 215 is less than 10 nm, advantageously less than 7 nm, andmore advantageously between 1 nm and 5 nm, as measured normal to the finsidewall (e.g., T₁ in FIG. 2B). In further embodiments, impurity sourcefilm 215 disposed over substrate surface layer 206 has substantially thesame thickness as along a fin sidewall (i.e., impurity source film 215has a substantially conformal thickness of T₁).

Impurity source film 215 is doped with the electrically impurity presentwithin the lower sub-fin region, such as, but not limited to,phosphorus, arsenic (n-type dopants of silicon) and boron (p-type dopantof silicon). In further embodiments, impurity source film 215 is aninsulative dielectric thin film, such as but not limited to, impuritydoped glasses. In certain such embodiments, impurity source film 215 isa boron-doped silicate glass (BSG), or phosphorus-doped silicate glass(PSG). Other options include a doped nitride, doped metallic film, dopedsemiconductor film, and the like. In an exemplary embodiment wheresubstrate 205 is substantially p-type silicon, impurity source film 215is doped with an impurity, such as phosphorus, that renders the lowersub-fin region n-type with a phosphorus impurity concentration ofbetween 10¹⁷ cm⁻³ and 10¹⁹ cm⁻3. Impurity source film 215 therefore hasa sufficiently high as-deposited impurity concentration and filmthickness to provide the desired impurity concentration within the lowersub-fin region. As one example, the impurity source film 215 is a 1-5 nmthick PSG film doped with phosphorus to 10²⁰−10²¹cm⁻³ and in directcontact with sidewalls of the fins 201, 202.

In embodiments, the sub-fin region further includes an upper sub-finregion proximate to the active region and associated with an incrementalfin sidewall height H₂. With the total sub-fin sidewall heightcorresponding to H₁+H₂, the proportioning of the sub-fin into the upperand lower regions may be varied through processing of the impuritysource films (e.g., 215). As shown in FIG. 2B, impurity source film 215is absent from the sidewall surfaces of the upper sub-fin regions 230A,230B, with at least one of an isolation dielectric 208 or a secondimpurity source film 235 disposed over impurity source film 215 and/oradjacent to the sidewall surfaces of the upper sub-fin regions of fins201, 202 (the isolation dielectric 208 is depicted as transparent inFIG. 2A to fully reveal impurity source films 215, 235). Where a secondimpurity source film is adjacent to the sidewall surfaces, as for theupper sub-fin region 230A, the upper sub-fin region is impurity dopedwith an impurity present in the second impurity source film. If anisolation dielectric is adjacent to the sidewall surface, as for theupper sub-fin region 230B, the upper sub-fin region may be substantiallyundoped where the isolation dielectric is advantageously substantiallyfree of the impurity present in first impurity source film 215 (as wellas substantially free of the impurity present in second impurity sourcefilm 235). Although not depicted, a substantially undoped cappingdielectric layer, such as silicon nitride, or the like, may be disposedbetween impurity source film 215 and impurity source film 235, and mayserve to limit intermixing of dopants between the impurity source films215 and 235 in regions where the impurity source film 235 is in contactwith the impurity source film 215.

Impurity source film 235 may serve as a solid-state diffusion dopantsource of an impurity, such as, but not limited to, phosphorus, arsenic,or boron. In an embodiment, upper sub-fin region 230A, and the secondimpurity source film 235 adjacent to sidewall surfaces of upper sub-finregion 230A, are doped with a second impurity that gives upper sub-finregion 230A a conductivity type complementary to that of lower sub-finregion 210A. Upper sub-fin doping may further render upper sub-finregion 230A doped distinctly from the overlying active fin region. Asone example, upper sub-fin region 230A is p-type when lower sub-finregion 210A is n-type. Upper sub-fin region 230A may be doped with animpurity concentration of between 10¹⁷ cm⁻³ and 10¹⁹ cm⁻³. Upper sub-findoping may serve one or more electrical functions, including awell-doping needed for a particular MOS structure as a function of theconductivity type of substrate 205; for threshold voltage tuning; or infurtherance of an isolation structure (e.g., to ensure a reverse diodeis present between the fin active region and the substrate). In theexemplary embodiment depicted in FIGS. 2A and 2B, fin 201, with theassociated doped sub-fin regions 210A and 230A, forms a portion of asubstrate-isolated NMOS transistor. Fin 202, with the associated dopedsub-fin regions 210B and 230B, forms a portion of a substrate-isolatedPMOS transistor. FIGS. 2A and 2B therefore illustrate finFET structurespresent in a monolithic CMOS circuit that may be implemented in a widevariety of integrated microelectronic devices.

In further embodiments, impurity source film 235 includes any of thematerials previously described as options for the impurity source film215. In certain such embodiments, impurity source film 235 is a samematerial as that of impurity source film 215, but complementarily doped.For example, impurity source film 235 may be a doped insulativedielectric thin film, such as but not limited to, impurity dopedglasses. In certain such embodiments, impurity source film 235 is aboron-doped silicate glass (BSG), or a phosphorus-doped silicate glass(PSG). Other options include a doped nitride, doped metallic film, dopedsemiconductor film, and the like. In an exemplary embodiment wheresubstrate 205 is substantially p-type silicon, and impurity source film215 is PSG, impurity source film 235 is silicate glass doped with animpurity, such as boron, that renders the upper sub-fin region 230Ap-type with a boron impurity concentration of between 10¹⁷cm⁻³ and 10¹⁹cm⁻3. Impurity source film 235 therefore has a sufficiently highas-deposited impurity concentration and film thickness to provide thedesired impurity concentration within upper sub-fin region 230A.Impurity source film 235 may have any thickness within the rangepreviously described for impurity source film 215. In an embodiment forexample, the impurity source film 235 is a 1-5 nm thick BSG film dopedwith boron to 10²⁰−10²¹cm⁻³ and in direct contact with sidewalls of thefins 201, 202 over the height Hz. In the exemplary embodimentillustrated in FIG. 2B, in regions where second impurity source film 235is disposed over impurity source film 215, impurity source film 215 hasa first sidewall thickness of T₁ that is greater than a second sidewallthickness T₂ in regions where isolation dielectric 208 is disposed overimpurity source film 215 (i.e., where impurity source film 235 isabsent).

In embodiments having a second impurity source film, isolationdielectric is disposed over both the first and the second impuritysource and may further backfill any spaces between sub-fin regions ofadjacent semiconductor fins. As shown in FIG. 2B for example, isolationdielectric 208 is disposed over impurity films 215 and 235 with a topsurface of isolation dielectric 208 being planar with impurity film 235to define the active region of fins 201, 202 as substantially equal toeach other (e.g., having a height H₃). Although not depicted, in certainembodiments isolation dielectric 208 may include multiple layers, suchas a silicon nitride liner, or the like, disposed in contact with one ormore of impurity source films 215 and 235, which may serve to limitoutward-diffusion of dopants from the impurity source films.

In embodiments, additional transistors disposed on the substratesimilarly include a semiconductor fin with upper and lower sub-finregions, however the upper and lower sub-fin regions are notcomplementarily doped, may be doped uniformly, or neither the uppersub-fin region, nor lower sub-fin region has an impurity dopingdeviating significantly from that of the substrate. Such transistorsthat lack any doping distinction between upper and lower sub-fin regionsmay lack any substrate isolation junction, but remain useful, forexample, in digital circuitry that is insensitive to substrate-couplednoise sources. Embodiments having some transistors with substrateisolation and others without substrate isolation may be found in certainSoC implementations. As illustrated by FIGS. 2A and 2D for example, withboth impurity source films 215 and 235 being absent from sidewallsurfaces of semiconductor fin 203, both lower sub-fin region 210C andupper sub-fin region 230C is of semiconductor substantially identical tothat of substrate 205. Similarly, substrate surface layer 210D has theconductivity the substrate 205 (e.g. p-type). With these structuralfeatures, fin 203 may form a portion of a non-substrate-isolated PMOStransistor, for example. Impurity source film 235 is however disposedadjacent to fin 204 and therefore upper sub-fin region 230D may have awell-type doping (e.g., p-type) substantially the same as that of uppersub-fin region 230A. Fin 204 may therefore form a portion of anon-substrate-isolated NMOS transistor, for example. FIGS. 2A and 2Btherefore illustrate finFET structures present in a monolithic CMOScircuit that may be implemented in a wide variety of mixed signal(analog and digital circuitry) integrated microelectronic devices, suchas a SoC. In the embodiment depicted in FIG. 2D lower sub-fin region210D is doped substantially the same as upper sub-fin region 230D (e.g.,both p-type) because impurity source 215 extends over the entire sub-finsidewall height H₁+H₂.

With a number of structural elements associated with exemplary finFETwell dopings by solid-state diffusion sources now described in detail,methods of fabricating such structures are further described inreference to the flow diagram in FIG. 3. In the illustratedimplementation, process 301 may include one or more operations,functions or actions as illustrated by one or more of operations 310,320, 330, 340, and/or 350. However, embodiments herein may include anynumber of operations such that some may be skipped. Further, variousembodiments may include additional operations not shown for the sake ofclarity.

The exemplary method 301 begins at operation 310 with receipt of asubstrate having semiconductor fin disposed thereon. For example, asubstrate with each of the fins 201-204 depicted in FIG. 2A may bereceived as an input starting material. As such fin structures may havebeen formed by any conventional means, no further description of theirfabrication is provided herein.

Method 301 proceeds to operation 320 where an impurity source film isformed adjacent to a sidewall of only a lower portion of the sub-finregion of at least one of the semiconductor fins. At operation 330 then,a film is formed adjacent to a sidewall of an upper portion of a sub-finregion for at least one of the fins. This second film may either be asecond impurity source film or an isolation dielectric film that issubstantially undoped, or at least lacks sufficient electrically activeimpurities to significantly alter the doping of an upper portion of thesub-fin region relative to the condition received at operation 310.

At operation 340, dopants from at least the impurity source filmdeposited at operation 320 are driven into the lower portion of thesub-fin region, for example to form a substrate-isolative junction. Anythermal process such as a furnace drive or rapid thermal anneal may beperformed to achieve sufficient solid-state diffusion that impuritiespresent in the impurity source film permeate the entire lateralthickness of the fin within the lower sub-fin region without diffusingfar up into the upper portion of the sub-fin region (e.g., by not morethan the lateral fin thickness, which may be 20-30 nm, or less). Method301 then completes with the formation of conventional aspects of adevice utilizing the active region of the fin disposed over the sub-finregion. In the exemplary embodiment, a gate stack and source/drains areformed to complete a MOS transistor structure using any techniquesconventional in the art.

FIG. 4 is a flow diagram further illustrating methods of forming anintegrated microelectronic device having a finFET architecture withmultiple solid-state diffusion sources for well doping, in accordancewith embodiments. Embodiments herein may include any number ofoperations such that some may be skipped. Further, various embodimentsmay include additional operations not shown for the sake of clarity.Such methods may, for example, be utilized to form one or more of thestructures depicted FIGS. 5A, 5B, 5C, 5D, 5E, 5F, 5G, 5H, 5I, and 5J,which are cross-sectional views of an evolving finFET as particularfabrication operations illustrated in FIG. 4 are performed to ultimatelyarrive at the architecture illustrated in FIGS. 2A-2D, in accordancewith an embodiment.

The exemplary method 401 begins at operation 410 with receiving asubstrate having a plurality of semiconductor fins. An exemplarystructure as received at operation 410 is illustrated in FIG. 5A. Any ofthe substrates and fin structures described elsewhere herein in thecontext of FIGS. 2A-2D may be received at operation 410 as an inputstarting material. At operation 415, the first impurity source film isdeposited over a sidewall of the fins. In the exemplary embodimentdepicted in FIG. 5B, the impurity source film 215 is depositedconformally over a fin sidewall 201A, over a fin top surface 201B, andover intervening surfaces of substrate 205. The deposition technique maydepend on the composition of impurity source film 215, with exemplarytechniques including chemical vapor deposition (CVD), atomic layerdeposition (ALD) and physical vapor deposition (PVD). The impuritysource film deposited at operation 415 may further have any of thecompositions and thickness previously described with 1-5 nm of PSGhaving a phosphorus doping of 10²⁰−10²¹cm⁻³being one specific exemplaryembodiment.

Returning to FIG. 4, method 401 proceeds to operation 420 where an etchmask is deposited and recessed over the first impurity source film toprotect the film adjacent to only a lower portion of the sub-fin region.FIG. 5C illustrates an exemplary etch mask 522 that is applied so as tobe planarized at a level above fins 201, 202. In one advantageousembodiment, etch mask 522 is any conventional photoresist applied byconventional techniques. Etch mask 522 may be other materials, orinclude one or more other materials, such as, but not limited to, anamorphous, or “diamond-like” carbon hardmask. After application of theetch mask, the etch mask may be optionally patterned by conventionaltechniques to remove the entire thickness of the etch mask in regions ofthe substrate where a substrate isolation doping of fins is not neededand/or desired. For example, a photoresist etch mask may belithographically patterned to selectively remove areas of the etch maskfrom portions of the substrate. Whether optionally patterned or inblanket form, the etch mask is then recessed selectively relative to thesemiconductor fins, or an intervening etch stop layer, so that the maskthen protects the underlying impurity source film only in regionsadjacent to the lower sub-fin region that is to be subsequently doped bythe impurity source film. FIG. 5D further depicts an exemplaryembodiment where the mask 522 is etched (developed) back by a dry or wetchemical process to a desired mask thickness corresponding to the finsidewall height H₁.

Returning to FIG. 4, at operation 425 a portion of the impurity sourcefilm not protected by the etch mask is removed selectively relative tothe semiconductor fins and interfacial (etch-stop) layer. Anyconventional etch may be employed at operation 425 depending on theimpurity source film composition. In the exemplary embodiment where theimpurity source film is PSG, any conventional wet or dry dielectric etchwith high selectivity to semiconductor may be utilized to arrive at thestructure depicted in FIG. 5D. Any regions where etch mask 522 wascompletely removed from a fin sidewall (e.g., by patterning the etchmask to unmask the first impurity source film adjacent to an upper andlower portion of a second sub-fin region of a second fin), impuritysource film 215 would be completely removed from the entire sub-finregion. Although, semiconductor surfaces of fins 201, 202 are exposed bythe etching of impurity source film 215 in the exemplary embodiment, anintervening etch stop layer may be exposed instead in the event thatimpurity source film 215 is not disposed directly on fins 201, 202.

Method 401 may then proceed to operation 430 where an optional pre-driveis performed. If performed, the impurities in the impurity source filmare driven into the lower portion of the sub-fin region. Temperature andtime parameters may be selected based on various factors, such as, butnot limited to, fin width, desired fin dopant concentration, andimpurity mobility within the impurity source film and/or semiconductorfin. An exemplary temperature range is 700-1100 C and an exemplary timerange is a few seconds to a few minutes for an exemplary fin width thatis less than 30 nm. The effects of such a pre-drive are illustrated inFIG. 5E, where dopants 520 are illustrated as having entered the lowerportion of the sub-fin region most proximate to impurity source film215, as well as into proximate regions of substrate 205.

Following the pre-drive, or where no pre-drive operation is performed,method 401 proceeds to operation 435 where a second impurity source filmis deposited over a sidewall of the fins. In the exemplary embodimentdepicted in FIG. 5F, impurity source film 235 is deposited conformallyover fins 201, 202 as well as over impurity source film 215 (ifpresent). For fins where impurity source film 215 had been previouslycompletely removed, impurity source film 235 may be in contact with theentire sidewall height of the fin (e.g., H_(fin)). The depositiontechnique employed at operation 435 may again depend on the compositionof impurity source film 235, with exemplary techniques including CVD,ALD, and PVD. Impurity source film 235 deposited at operation 435 mayfurther have any of the compositions and thickness previously describedwith 1-5 nm of BSG having a boron doping of 10²⁰−10²¹ cm⁻³ being onespecific exemplary embodiment.

Method 401 proceeds with masking at least one fin at operation 440 andremoving the exposed portion of the second Impurity source film. Anyconventional photoresist etch mask, photolithographic patterning of theetch mask, and subsequent etching of the underlying impurity film may beperformed at operation 440. As further depicted in FIG. 5G, a portion ofretained impurity source film 235 may be disposed over impurity sourcefilm 215 having the thickness T₁ while removal of the impurity sourcefilm 235 in other regions reduces the thickness of impurity source film215 to a second thickness T₂, as a function of the etch selectivitybetween the two impurity source films 235, 215. For the exemplaryembodiment where impurity source film 235 is BSG and impurity sourcefilm 215 is PSG, etch selectivity may be made very high with properchoice of etchant chemistry so the difference between T₁ and T₂ may beonly a few nm, or may even be imperceptible. A greater distinctionbetween T₁ and T₂ may be visible for other material systems and/orremoval processes. For fins where impurity source film 215 had beenpreviously completely removed, impurity source film 235 may be alsocompletely removed from the fin semiconductor.

Returning to FIG. 4, at operation 450 isolation dielectric is formedover any impurity source films present (e.g., the first and secondimpurity source films formed at operations 415 and 435). Isolationdielectric may be formed through any conventional techniques, forexample with a gap filling dielectric deposition process andplanarization polish, etc. At operation 455, the isolation dielectric isthen recessed selectively to the semiconductor fins and/or anintervening stop layer to define an active region of the fins. Anyconventional isolation recess process may be utilized to achieve theintermediate structure shown in FIG. 5H where fins 201, 202 have activeregions extending a sidewall height H₃ from a top surface of isolationdielectric 208. In conjunction with the sidewall height H₁ as wasdefined by the etch mask recessing that was performed at operation 420,the exposed surface of isolation dielectric 208 further defines asidewall height H₂ over which impurity source film 235 (if present) isadjacent to an upper portion of the sub-fin region. Where both impuritysource films 215, 235 had been previously completely removed, recessingof isolation dielectric 208 defines the active region from a sub-finregion that is to have substantially the same impurity doping as thesubstrate. Where impurity source film 235 was retained, but impuritysource film 215 was removed, recessing of isolation dielectric 208defines the active region from a sub-fin region that is to have ahomogeneous doping of the impurity in impurity source film 235.

Continuing at operation 460 (FIG. 4) with the sub-fin and active regionsnow defined, impurities from impurity source films are driven intodistinct portions of the fin most proximate to the impurity sourcefilms. Operation 460 may entail any elevated temperature process knownin the art to be suitable to enhance diffusion of dopants from thesource film(s) into the adjacent semiconductor. Temperature and timeparameters may be selected based on various factors, such as, but notlimited to, fin width, desired fin doping concentration, whetherpre-drive operation 430 had been previously performed, and impuritymobility within the impurity source film(s) and/or semiconductor fin. Anexemplary temperature range is 700-1100 C and an exemplary time range isa few seconds to a few minutes for an exemplary fin width that is lessthan 30 nm. As shown in FIG. 5I, the drive operation 460 dopes uppersub-fin region 230A with a second impurity. Where multiple impuritysource films are adjacent to distinct portions of the sub-fin region thedrive operation 460 dopes the distinct portions of the sub-fin regionwith impurities from the various localized impurity source films. Forexample, where impurity source film 215 is PSG and impurity source film235 is BSG, the upper sub-fin region is doped to a conductivity typecomplementary to that of the lower sub-fin region 210A.

Method 401 then completes with conventional transistor fabricationoperations, such as, but not limited to forming a gate stack and asource/drain for each active region of the fins, and interconnecting thegate stacks and source/drains, for example to form CMOS circuitry usingone or more of substrate-isolated or non-substrate-isolated finstructures. In the exemplary embodiment depicted in FIG. 5J, formationof the gate stack 260 and source/drains arrives at the structure 200,possessing one or more of the features previously described elsewhereherein in the context of FIGS. 2A-2D.

FIG. 6 illustrates a system 1000 in which a mobile computing platform1005 and/or a data server machine 1006 employs a monolithic IC withimpurity source films adjacent to impurity doped sub-fin regions, inaccordance with embodiments of the present invention. The server machine1006 may be any commercial server, for example including any number ofhigh performance computing platforms disposed within a rack andnetworked together for electronic data processing, which in theexemplary embodiment includes a packaged monolithic IC 1050. The mobilecomputing platform 1005 may be any portable device configured for eachof electronic data display, electronic data processing, wirelesselectronic data transmission, or the like. For example, the mobilecomputing platform 1005 may be any of a tablet, a smart phone, laptopcomputer, etc., and may include a display screen (e.g., a capacitive,inductive, resistive, touchscreen), a chip-level or package-levelintegrated system 1010, and a battery 1015.

Whether disposed within the integrated system 1010 illustrated in theexpanded view 1020, or as a stand-alone packaged chip within the servermachine 1006, packaged monolithic IC 1050 includes a memory chip (e.g.,RAM), or a processor chip (e.g., a microprocessor, a multi-coremicroprocessor, graphics processor, or the like) employing a monolithicarchitecture with at least one finFET having an impurity doped sub-finregion adjacent to an impurity source film, and advantageously includesa SoC architecture with at least one finFET having a substrate isolationdoped lower sub-fin region and at least one other finFET having a lowersub-fin region without such isolation doping. The monolithic IC 1050 maybe further coupled to a board, a substrate, or an interposer 1060 alongwith, one or more of a power management integrated circuit (PMIC) 1030,RF (wireless) integrated circuit (RFIC) 1025 including a wideband RF(wireless) transmitter and/or receiver (TX/RX) (e.g., including adigital baseband and an analog front end module further comprises apower amplifier on a transmit path and a low noise amplifier on areceive path), and a controller thereof 1035.

Functionally, PMIC 1030 may perform battery power regulation, DC-to-DCconversion, etc., and so has an input coupled to battery 1015 and withan output providing a current supply to other functional modules. Asfurther illustrated, in the exemplary embodiment, RFIC 1025 has anoutput coupled to an antenna (not shown) to implement any of a number ofwireless standards or protocols, including but not limited to Wi-Fi(IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE 802.20, long termevolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE, GSM, GPRS, CDMA,TDMA, DECT, Bluetooth, derivatives thereof, as well as any otherwireless protocols that are designated as 3G, 4G, 5G, and beyond. Inalternative implementations, each of these board-level modules may beintegrated onto separate ICs coupled to the package substrate of themonolithic IC 1050 or within a single IC coupled to the packagesubstrate of the monolithic IC 1050.

FIG. 7 is a functional block diagram of a computing device 1100,arranged in accordance with at least some implementations of the presentdisclosure. Computing device 1100 may be found inside platform 1005 orserver machine 1006, for example, and further includes a motherboard1102 hosting a number of components, such as but not limited to aprocessor 1104 (e.g., an applications processor), which may incorporatelocal inter-level interconnects as discussed herein, and at least onecommunication chip 1106. In embodiments, at least one of the processor1104 one or more communication chips 1106, or the like. Processor 1104may be physically and/or electrically coupled to motherboard 1102. Insome examples, processor 1104 includes an integrated circuit diepackaged within the processor 1104. In general, the term “processor” or“microprocessor” may refer to any device or portion of a device thatprocesses electronic data from registers and/or memory to transform thatelectronic data into other electronic data that may be stored inregisters and/or memory.

In various examples, one or more communication chips 1106 may also bephysically and/or electrically coupled to the motherboard 1102. Infurther implementations, communication chips 1106 may be part ofprocessor 1104. Depending on its applications, computing device 1100 mayinclude other components that may or may not be physically andelectrically coupled to motherboard 1102. These other componentsinclude, but are not limited to, volatile memory (e.g., DRAM),non-volatile memory (e.g., ROM), flash memory, a graphics processor, adigital signal processor, a crypto processor, a chipset, an antenna,touchscreen display, touchscreen controller, battery, audio codec, videocodec, power amplifier, global positioning system (GPS) device, compass,accelerometer, gyroscope, speaker, camera, and mass storage device (suchas hard disk drive, solid-state drive (SSD), compact disk (CD), digitalversatile disk (DVD), and so forth), or the like.

Communication chips 1106 may enable wireless communications for thetransfer of data to and from the computing device 1100. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. Communication chips 1106 may implement anyof a number of wireless standards or protocols, including but notlimited to those described elsewhere herein. As discussed, computingdevice 1100 may include a plurality of communication chips 706. Forexample, a first communication chip may be dedicated to shorter-rangewireless communications, such as Wi-Fi and Bluetooth, and a secondcommunication chip may be dedicated to longer-range wirelesscommunications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, andothers.

While certain features set forth herein have been described withreference to various implementations, this description is not intendedto be construed in a limiting sense. Hence, various modifications of theimplementations described herein, as well as other implementations,which are apparent to persons skilled in the art to which the presentdisclosure pertains are deemed to lie within the spirit and scope of thepresent disclosure.

It will be recognized that the invention is not limited to theembodiments so described, but can be practiced with modification andalteration without departing from the scope of the appended claims. Forexample, the above embodiments may include specific combination offeatures.

In one exemplary embodiment, an integrated microelectronic devicecomprises a substrate. A first transistor including a non-planarsemiconductor fin extends from the substrate. The fin has a sub-finregion disposed between an active region of the fin and the substrate,wherein the sub-fin region further comprises a lower sub-fin regionproximate to the substrate and an upper sub-fin region proximate to theactive region. A first impurity source film is disposed adjacent to asidewall surface of the lower sub-fin region, but is absent from theupper sub-fin region. The first impurity source film is doped with animpurity present in the lower sub-fin region. A gate stack is disposedadjacent to a sidewall surface of the active region.

In a further embodiment, the device further comprises a dielectricdisposed over the first impurity source film and adjacent to a sidewallsurface of the upper sub-fin region. The isolation dielectric issubstantially free of the impurity present in the first impurity sourcefilm.

In a further embodiment, the device further comprises a second impuritysource film that comprises a second impurity and is disposed over thefirst impurity source film and is adjacent to a sidewall surface of theupper sub-fin region. The upper sub-fin region is doped with the secondimpurity to have a conductivity type complementary to that of the lowersub-fin region.

In a further embodiment, the device further comprises a second impuritysource film comprising a second impurity and is disposed over the firstimpurity source film and adjacent to a sidewall surface of the uppersub-fin region. The upper sub-fin region is doped with the secondimpurity to have a conductivity type complementary to that of the lowersub-fin region. A second transistor including a second non-planarsemiconductor fin extends from the substrate, the second fin has asecond sub-fin region disposed between a second active region of thesecond fin and the substrate. The second sub-fin region furthercomprises a second lower sub-fin region proximate to the substrate and asecond upper sub-fin region proximate to the second active region. Thefirst impurity source film is further disposed adjacent to a sidewallsurface of the second lower sub-fin region, but is absent from thesecond upper sub-fin region. An isolation dielectric is disposed overthe first impurity source film and adjacent to a sidewall surface of thesecond upper sub-fin region. The isolation dielectric is substantiallyfree of the impurities present in the first or second impurity sourcefilms.

In further embodiments, for any of the device embodiments describedabove, the lower sub-fin region has an impurity doping distinct fromthat of the upper sub-fin region and the first impurity source filmcomprises the impurity of the lower sub-fin region.

In further embodiments, for any of the device embodiments describedabove, the lower sub-fin region is doped with the impurity to have aconductivity type complementary to that of the substrate.

In further embodiments, for any of the device embodiments describedabove, the upper sub-fin region has an impurity doping distinct fromboth the lower sub-fin region and the active fin region.

In further embodiments, for any of the device embodiments describedabove, the upper sub-fin region has an impurity doping complementary tothe lower sub-fin region.

In further embodiments, for any of the device embodiments describedabove, the first fin has a lateral width less than 20 nm, extends upfrom the substrate by 20-150 nm. The first impurity source filmcomprises a silicate glass film having a thickness between 1 nm and 7nm. The lower sub-fin region has a dopant concentration between 10¹⁷cm⁻³ and 10¹⁹ cm⁻³.

In further embodiments, for any of the device embodiments describedabove, a third transistor including a third non-planar semiconductor finextending from the substrate. The third fin has a third sub-fin regiondisposed between a third active region of the third fin and thesubstrate. The third sub-fin region further comprises a third lowersub-fin region proximate to the substrate and a third upper sub-finregion proximate to the third active region. The first impurity sourcefilm is absent from sidewall surfaces of the third lower sub-fin regionand third upper sub-fin region. A second impurity source film is furtherdisposed adjacent to a sidewall surface of the upper sub-fin region.

In further embodiments, a device includes a second impurity source filmcomprising second impurity source film disposed over the first impuritysource film and adjacent to a sidewall surface of the upper sub-finregion. The upper sub-fin region is doped with boron. A secondtransistor includes a second non-planar semiconductor fin extending fromthe substrate, the second fin having a second sub-fin region disposedbetween a second active region of the second fin and the substrate. Thesecond sub-fin region further comprises a second lower sub-fin regionproximate to the substrate and a second upper sub-fin region proximateto the second active region. The first impurity source film is furtherdisposed adjacent to a sidewall surface of the second lower sub-finregion and absent from the second upper sub-fin region. An isolationdielectric is disposed over the first impurity source film and adjacentto a sidewall surface of the second upper sub-fin region. The isolationdielectric is substantially free of the impurities present in the firstor second impurity source films. A second gate stack is disposedadjacent to a sidewall surface of the second active region, over theisolation dielectric. A third transistor includes a third non-planarsemiconductor fin extending from the substrate. The third fin has athird sub-fin region disposed between a third active region of the thirdfin and the substrate. The first impurity source film is absent fromsidewall surfaces of the third sub-fin region. A second impurity sourcefilm is further disposed adjacent to a sidewall surface of the thirdsub-fin region. A third gate stack is disposed adjacent to a sidewallsurface of the third active region. The first and third transistors areNMOS transistors and the second transistor is a PMOS transistor. Thefirst and second impurity source films each comprise a doped silicateglass. The first and second lower sub-fin regions are doped n-type. Asurface layer in a first region of the substrate separating the firstand second lower sub-fin regions is doped n-type. A sub-surface regionof the substrate disposed below the surface layer in the first region,and a surface layer in a second region of the substrate separating thethird sub-fin region from the first and second lower sub-fin regions,are doped p-type.

In embodiments a mobile computing platform, comprises the device of anyof exemplary embodiments above, a display screen communicatively coupledto the device, and a wireless transceiver communicatively coupled to thedevice.

In embodiments, a method of fabricating an integrated microelectronicdevice comprises receiving a non-planar semiconductor fin, forming animpurity source film, forming a second film over the impurity sourcefilm, driving dopants from the impurity source film, and forming a gatestack and a source/drain. The non-planar semiconductor fin is formedextending from a substrate, with a sub-fin region disposed between anactive region of the fin and the substrate. The impurity source film isformed adjacent to a sidewall of a lower portion of the sub-fin regionproximate to the substrate. The second film is formed over the impuritysource film and adjacent to a sidewall of an upper portion of thesub-fin region proximate to the active region. The dopants are drivenfrom the impurity source film into the lower portion of the sub-finregion. The gate stack and a source/drain are formed over the activeregion.

In further embodiments, forming the impurity source film furthercomprises depositing the impurity source film over a sidewall the fin,forming and recessing an etch mask over the impurity source film toprotect the impurity source film adjacent to the lower portion of thesub-fin region, and removing an unmasked portion of the first impuritysource film prior to the driving.

In further embodiments, forming the second film over the impurity sourcefilm further comprises forming a second impurity source film comprisinga second impurity over the first impurity source film and adjacent to asidewall surface of the upper sub-fin region. The driving dopes theupper sub-fin region with the second impurity to have a conductivitytype complementary to that of the lower sub-fin region.

In further embodiments, receiving a non-planar semiconductor finextending from a substrate further comprises receiving a plurality ofnon-planar semiconductor fins, the fins each having a sub-fin regiondisposed between an active region of the fin and the substrate. In theseembodiments, forming a second impurity source film further comprisesdepositing a second impurity source film over a sidewall of theplurality of fins. At least one of the fins is then masked. An unmaskedportion of the second impurity source film is removed. An isolationdielectric is formed over the first and second impurity source films.The isolation dielectric and second impurity source film is recessed toexpose the active fin region. The driving dopes portions of the sub-finregions with impurities from first and second impurity source films.

In further embodiments, the impurity source film dopes the lower sub-finregion to have a conductivity type complementary to that of thesubstrate.

In any of the above exemplary embodiments, receiving a non-planarsemiconductor fin extending from a substrate further comprises receivinga plurality of non-planar semiconductor fins, the fins each having asub-fin region disposed between an active region of the fin and thesubstrate. Forming and recessing the etch mask over the impurity sourcefilm further comprises patterning the etch mask to unmask the firstimpurity source film adjacent to an upper and lower portion of a secondsub-fin region of a second fin, and removing the unmasked portion of thefirst impurity source film prior to the driving.

Exemplary embodiments further include a method of forming a system on achip (SoC). A plurality of non-planar semiconductor fins extending froma substrate are received, each fin having a sub-fin region disposedbetween an active region of the fin and the substrate. Fins in a firstregion of the substrate are electrically isolated from fins in a secondregion of the substrate, by depositing a first impurity source film overa sidewall the fins. A first etch mask is deposited over the firstimpurity source film. The first etch mask is patterned to protect thefirst impurity source film adjacent to the first and second fins andexpose the first impurity source film adjacent to the third fin. Thepatterned first etch mask is recessed to protect only the impuritysource film adjacent to a lower portion of the sub-fin region. Theunmasked portions of the first impurity source film are removed.Impurities are driven from the first impurity source film into the lowerportion of the sub-fin regions. A complementary well is formed in aportion of the first substrate region, by depositing a second impuritysource film over a sidewall of the plurality of fins. A second etch maskis patterned to protect the second impurity source film adjacent to thefirst fin and expose the second impurity source film adjacent to thesecond fin. Unmasked portions of the second impurity source film areremoved. An isolation dielectric is formed over the first and secondimpurity source films. The isolation dielectric and second impuritysource film are recessed to expose active regions of the fins.Impurities are driven from the second impurity source film into an upperportion of the sub-fin region. CMOS circuitry is fabricated within thefirst and second substrate regions by forming a gate stack and asource/drain for each active region of the fins, and interconnecting thegate stacks and source/drains.

In further embodiments, a complementary well is formed in a portion ofthe second substrate region by patterning the second etch mask toprotect the second impurity source film adjacent to the third fin.

However, the above embodiments are not limited in this regard and, invarious implementations, the above embodiments may include theundertaking only a subset of such features, undertaking a differentorder of such features, undertaking a different combination of suchfeatures, and/or undertaking additional features than those featuresexplicitly listed. The scope of the invention should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

What is claimed is:
 1. A structure comprising: a fin comprising siliconand including a first region over a second region; a gate stack adjacentto a sidewall surface of the first region, wherein the gate stackincludes a gate dielectric and a gate electrode; a source and a drain; adielectric layer adjacent to a sidewall surface of the second region,wherein the dielectric layer comprises an impurity that is also presentwithin the second region and associated with a conductivity type; and anisolation material adjacent to the dielectric layer.
 2. The structure ofclaim 1, wherein: the dielectric layer comprises a phosphorus-dopedsilicate glass (PSG); the impurity is phosphorus; and the fin isassociated with a PMOS transistor.
 3. The structure of claim 1, whereinthe dielectric layer is in contact with at least one of the gateelectrode or gate dielectric.
 4. The structure of claim 1, wherein: thefirst region has a lateral width less than 20 nm; the fin has a verticalheight of between 20 nm and 150 nm; and the dielectric layer has athickness between 1 nm and 5 nm as measured normal to the sidewallsurface.
 5. The structure of claim 1, wherein the dielectric layer has asubstantially conformal thickness.
 6. The structure of claim 1, furthercomprising a second fin, wherein: the second fin includes an upperregion and a lower region; a second gate stack is adjacent to a sidewallsurface of the upper region; and a second source and drain are coupledto the upper region; a second dielectric layer is adjacent to a sidewallsurface of the lower region, wherein the second dielectric layercomprises a second impurity that is also present within the lower regionand is associated with a second, complementary, conductivity type; andthe isolation material is separating the first dielectric layer from thesecond dielectric layer.
 7. The structure of claim 6, wherein theisolation material comprises a plurality of dielectric layers includinga silicon nitride layer that is adjacent to the first dielectric layerand the second dielectric layer.
 8. The structure of claim 6, wherein:the first dielectric layer comprises a phosphorus-doped silicate glass(PSG); the fin is associated with a PMOS transistor; the seconddielectric layer comprises a boron-doped silicate glass (BSG); and thesecond fin is associated with an NMOS transistor.
 9. The structure ofclaim 8, wherein: the first dielectric layer and second dielectric layerform a stack of layers adjacent to a sidewall surface of at least one ofthe second region of the fin, or lower region of the second fin.
 10. Thestructure of claim 9, wherein the stack of layers further comprises asilicon nitride layer between the first and second dielectric layers.11. The structure of claim 6, wherein the first region comprises thefirst impurity at a concentration of between 10e17 and 10e19 cm−3. 12.The structure of claim 11, wherein the lower region comprises the secondimpurity at a concentration of between 10e17 and 10e19 cm−3.
 13. Thestructure of claim 1, wherein the dielectric layer comprising theimpurities extends over a substrate surface that intersects the sidewallsurface of the second region, the dielectric layer over the substratesurface separating the isolation dielectric from the substrate surface.14. A structure, comprising: a PMOS transistor, further comprising: afirst fin comprising silicon and including a first region over a secondregion; a gate stack adjacent to a sidewall surface of the first region,wherein the gate stack includes a gate dielectric and a gate electrode;a source and a drain; and a first dielectric layer comprising phosphorusand silicon adjacent to a sidewall surface of the second region, whereinphosphorus is also present within the second region; an NMOS transistor,further comprising: a second fin comprising silicon and including anupper region over a lower region; a gate stack adjacent to a sidewallsurface of the upper region, wherein the gate stack includes a gatedielectric and a gate electrode; a source and a drain; and a seconddielectric layer comprising boron and silicon adjacent to a sidewallsurface of the second region, wherein boron is also present within thelower region; and an isolation material separating the first fin fromthe second fin, wherein the isolation material is adjacent to the firstdielectric layer and adjacent to the second dielectric layer.
 15. Thestructure of claim 14, wherein: the first region has a lateral widthless than 20 nm; the fin has a vertical height of between 20 nm and 150nm; and the first dielectric layer has a thickness between 1 nm and 5 nmas measured normal to the sidewall surface.
 16. The structure of claim14, wherein the isolation material comprises a plurality of dielectriclayers including a silicon nitride layer that is adjacent to the firstdielectric layer and the second dielectric layer.
 17. The structure ofclaim 14, wherein: the first region comprises phosphorus at aconcentration of between 10e17 and 10e19 cm−3; and the lower regioncomprises boron at a concentration of between 10e17 and 10e19 cm−3. 18.A structure comprising: a fin comprising silicon and including a firstregion over a second region; a gate stack adjacent to a sidewall surfaceof the first region, wherein the gate stack includes a gate dielectricand a gate electrode; a source and a drain; and a dielectric layercomprising boron and silicon adjacent to a sidewall surface of thesecond region, wherein boron is also present within the second region.19. The structure of claim 18, further comprising a second fin, wherein:the second fin includes an upper region and a lower region; a secondgate stack is adjacent to a sidewall surface of the upper region; and asecond source and drain are coupled to the upper region; a seconddielectric layer comprising phosphorus and silicon is adjacent to asidewall surface of the lower region, wherein phosphorus is also presentwithin the second region; and an isolation material is separating thefirst dielectric layer from the second dielectric layer.
 20. Thestructure of claim 18, wherein the first dielectric layer and seconddielectric layer form a stack of layers adjacent to a sidewall surfaceof at least one of the second region of the fin, or lower region of thesecond fin.